1. Field of the Invention
The present invention relates generally to the field of electrical discharge machining and more particularly to an improved apparatus for abrasively forming electrical discharge machining electrodes.
2. Description of the Prior Art
Prior to the present invention a method and apparatus for forming electrical discharge machining electrodes were disclosed in U.S. Pat. No. 3,663,785 entitled Method of Erosively Shaping a Master Die and U.S. Pat. No. Re. 27,588 entitled Apparatus for Shaping Electrodes, respectively. The method and the apparatus for its implementation involved the use of an abrasive die and an electrode workpiece mounted in working alignment with one another. The die and workpiece are moved relative to one another in a horitzontal oscillatory rotary motion as they are brought together in the vertical direction such that the workpiece is abrasively formed into the same shape and contour as the die member.
In order to accommodate the need to operate the abrading apparatus at different amplitudes of oscillatory rotary motion it was necessary that the eccentricity of the two drive spindles be adjustable. This was accomplished by mounting the eccentric pin of each spindle to the platen to be oscillated with opposed locking wedges. In order to effect an adjustment of the oscillation amplitude the mounting assembly for each drive spindle had to be separately loosened and the opposed wedges moved relating to one another to increase or decrease the offset of the eccentric pin axis from the main rotational axis of the spindle. Since each spindle had to be individually adjusted the adjustment process required an experienced and skilled operator to assure that both spindles were set to the same measure of offset as well as the same point in rotation. Excessive set-up time was thus involved and even minor errors would lead to excessive bearing wear during operation. The overall assembly was, furthermore, much less rigid then required for precision operation.